| 摘要 |
PROBLEM TO BE SOLVED: To provide a novel method and a device capable of detecting not only the number of particulates contained in a test liquid but also a particle size distribution of the particulates and the like. SOLUTION: In a turbidity detecting method wherein a light beam from a coherent light source is condensed once on a prescribed focal point to form a radial light beam, wherein the test liquid is passed along a direction orthogonal to an optical axis of the radial light beam inside the light beam in the vicinity of the focal point, wherein a change of diffracted light generated in the light beam by the existence of the particulates in the test liquid is detected by a photodetector arranged on an optical path for the light beam in an opposite side of the light source with respect to the fluid, to be converted into an electric signal, and wherein the particulates contained in the test liquid are detected based on a change of the electric signal, a distance between a particulate-passing locus and the focal point is detected by measuring a time required for passing of the particulate in the test liquid across the light beam, and a particle size of the particulate is calculated based on the distance, in this method for measuring the particle size of the fine particulate in the fluid.
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